1. Field of the Invention
The present invention relates to systems and methods for determining the locations of objects and more particularly to deriving the environment and the locations and movements of objects without the use of a specific interrogation signal, thereby providing situational awareness.
2. Description of the Related Art
There is an attempt to increase the lethality of vehicles of Future Combat Systems, “Objective Force” by the use of speed and agility. This requires thin skinned armor which increases the vulnerability to conventional weapons of all types. To counter this weakness, in present systems the use of Unmanned Ground Sensors (UGS) must be deployed ahead of the Objective Force vehicles to provide them situational awareness of potential enemies. If the UGS cannot be deployed then the Objective Force cannot risk being utilized.
As will be disclosed below the present invention provides for minimizing the dependency on UGS for deployment of the Objective Force and other thin skinned armor forces. U.S. Pat. No. 6,580,392, entitled “Digital Beamforming for Passive Detection of Target Using Reflected Jamming Echoes” discloses a radar system and method for detecting and tracking a target of interest in the presence of interference, wherein the interference emits interfering signals, includes a receiver for receiving the interfering signals directly from the interference. The receiver also receives reflected signals, wherein the reflected signals are the interfering signals reflected by the target of interest. The interfering signals and the reflected signals are compared to detect the target of interest. In one embodiment, the reflected signals and the interfering are cross-correlated. The results of the cross-correlation are used to obtain range, position, and velocity information about the target of interest from a range/Doppler map. The '392 system relies on the enemy to emit hostile Damming) signals.
Conventional art solves this where the friendly object actively transmits a radar signal and receives its reflection. The disadvantage is that a directional antenna is needed in conjunction with microwave frequencies which are easier to hide from via stealthy technologies. As will be disclosed below, the lower VHF and UHF communications frequencies, which are likely utilized with the present invention, are practically impossible to hide from using stealth technologies.